1. Field of the Invention
The present invention relates to an improved process for treating a ply-twisted crimped multifilament yarn. More particularly, the process involves adjusting the temperature and moisture content of the yarn prior to passing the yarn through a stuffing chamber. These yarns are especially suitable for producing textured saxony-type carpets having a tightly tailored surface texture.
2. Description of the Related Art
A large portion of carpets used in residences are known as cut pile carpets which include saxony-type carpets. In saxony-type carpets, heat-set, ply-twisted pile yarn is inserted into a backing material as loops which are then cut to form vertical tufts. The tufts are then evenly sheared to a desired height which is typically about 0.4 to 0.7 inches. Generally, there are two different styles of saxony-type carpets: 1) a straight-set style in which the filaments at the tuft tip are straight and substantially perpendicular to the plane of the carpet face, and 2) a textured style in which the tufts and the individual filaments have varying degrees of curl.
Yarn which is used as pile in textured saxony-type carpets is prepared by cabling together two or more singles yarns, heat-setting them in their twisted condition, and finally drying them. One known method of processing the ply-twisted yarn involves feeding the yarn through a stuffing chamber and then passing the yarn through a continuous heat-setting machine known as a Superba.RTM. which treats the yarn with pressurized saturated steam to heat-set the twist. The yarn is axially compressed within the stuffing chamber. Another known method involves feeding the ply-twisted yarn through the stuffing chamber and then passing it through a continuous heat-setting machine known as a Suessen which treats the yarn with dry heat to heat-set the twist. The yarn is tufted into a carpet backing material, and the carpet is subjected to standard dyeing and finishing operations including stain and soil resist treatment.
Depending upon the twist level of the yarns and other factors, textured saxony-type carpets may exhibit different surface textures. For example, a frieze carpet is made from pile yarns having a "high ply-twist". By the term "high ply-twist" as used herein, it is meant a ply-twist level of greater than about 5.5 turns per inch (tpi). When such yarn is processed and then tufted into a backing material, the resulting carpet tufts are highly kinked and curled. This gross buckling of the tuft structure gives the carpet a distinct texture.
In other instances, textured saxony-type carpets may have a looser surface texture, where the tips of the tufts are splayed open and the carpet surface has a brush-like appearance. This type of texture is similar to the texture of a straight-set saxony-type carpet. Generally, these carpets are made from "low ply-twist" pile yarns. By the term "low ply-twist" as used herein, it is meant a ply-twist level of less than about 4.25 turns per inch (tpi).
Other textured saxony-type carpets containing low ply-twist pile yarns have a poodle-like surface texture, where many of the tufts have an initial unraveled structure. These carpets may also be referred to as being overtextured. Often, the yarns for these carpets are processed by injecting steam directly into the stuffing chamber as the yarn passes through the chamber.
Another type of desirable surface texture is referred to as a "tightly tailored" texture. By the term "tightly tailored" as used herein, it is meant a surface texture characterized by substantially straight and unkinked tufts having a tightly twisted structure, with high twist integrity. The tuft tips are substantially unopened and have compact helical curls, and the tuft structures do not demonstrate gross buckling. Such carpets may also be referred to as "trackless" carpets, since they tend to show reduced footprints and vacuum cleaning marks.
In the past, high ply-twist nylon 6 and nylon 6,6 yarns were typically used to achieve this tightly tailored appearance. However, the need for initial higher twisting in the yarns makes these yarn manufacturing processes slow and less economically viable.
Now, in accordance with this invention, it has been found that textured saxony-type carpets having a tightly tailored surface texture may be prepared from nylon 6,6 yarns having lower twist levels than nylon 6,6 yarns used in the past. These carpets are prepared from yarns produced by the unique process of this invention.